This commit adds the upgrade guide from ScyllaDB Open Source 5.4 to ScyllaDB Enterprise 2024.1. The need to include the "Restore system tables" step in rollback has been confirmed; see https://github.com/scylladb/scylladb/issues/11907#issuecomment-1842657959 Fixes https://github.com/scylladb/scylladb/issues/16445